This invention relates to apparatus for analyzing the size distribution and quantity of small particles in an aerosol.
Compliance with regulations governing maximum emission values, so-called MAK-values, to combat air pollution call for the provision of suitable measuring techniques (local and remote measurements). Local measurement should be simple and capable of being continuously performed for analyzing the particle size distribution in the aerosol, and at least they should be capable of discriminating between coarse and invasive fine pulmonary dusts with the necessary sensitivity.
It is the general practice to make use of instruments based on the light scattering effect of suspensoids, or of centrifuges or filters.
Commercial diffusion measuring instruments are technically complex and they fail to detect very small particles. On the other hand, they generate an electrical signal which is convenient to evaluate.
Centrifuges have very high resolution powers, but the measurement (weighing) requires the collection of a large amount of material and is difficult to perform.
Sampling by means of filters is an easy method, but for the measurement of a precipitate by weighing a large amount of material is likewise required. Moreover, some filters do not discriminate between the precipitated particle sizes.
These known measuring techniques are not therefore capable of meeting all the requirements for solving the contemplated problem.